Re: REBASE_HEAD still exists after success end rebase

I made a very short-lived effort to look into why this "bug" was
happening.  I say "bug" in quotes, because I'm not even sure if it is
even problematic behavior.

I think this is a bug because git create similar HEADs if you made merge 
or cherry-pick. I don't have problems with them.

Plus by git rebase docs on official site flag '--show-current-patch':
---
Show the current patch in an interactive rebase or when rebase is 
stopped because of conflicts. This is the equivalent of git show 
REBASE_HEAD.
---
For me it means that return patch only if rebase in progress - not 
aborted/not complete/have conflicts

I solved my need at the time (detecting a rebase in progress) by
checking for the existence of either of the 'rebase-merge' or
'rebase-apply' directories in $GIT_DIR.

Thanks for advice! I don't knew it.